The disaster management office revised the number of people trapped since Sunday morning in the tunnel in Uttarakhand state to 41, up from 40.
A rescue mission is currently underway at the Silkyara tunnel in Uttarakhand to free 41 workers who are stuck inside following a landslide.
Authorities have not said what caused the 4.5-km (3-mile) tunnel to cave in, but the region is prone to landslides, earthquakes and floods.
Work was suspended on Friday after a "large-scale cracking sound" was heard as rescue workers sought to restart the drilling machine, according to a report from NHIDC.
Close to 100 tunnel workers gathered at the site on Saturday, demanding faster progress in reaching and freeing those trapped.
Persons:
Shankar Prasad Nautiyal, Anshu Malik Halko, Halko, Vishnu Sahu, Sahu, Saurabh Sharma, Ira Dugal, William Mallard, Tom Hogue
Organizations:
REUTERS, Highways, Infrastructure Development Corporation, Reuters, Authorities, Thomson
Locations:
Uttarkashi, Uttarakhand, India, Madhya Pradesh